A picture such as a subtitle (this picture is hereinafter referred to as the sub picture) may be superimposed with a picture of content (this picture is hereinafter referred to as the main picture) and the superimposed pictures are displayed so as to supplement the main picture.
Normally, the aspect ratio of the sub picture is associated with that of the main picture. When the aspect ratio of the main picture with which the sub picture is superimposed is a:b, the aspect ratio of the sub picture is set to a:b. When the aspect ratio of the main picture with which the sub picture is superimposed is c:d, the aspect ratio of the sub picture is set to c:d.
As a specific example, when the aspect ratio of the display device is 16:9 and that of the main picture is 4:3, as shown in FIG. 1, the picture frame size of the main picture is changed and data that cause the left and right end areas of the screen to become black are added. At this point, the subtitle is normally displayed with an aspect ratio of 4:3 (see Patent Document, Japanese Patent Application Laid-Open No. HEI 10-308924).
However, in a small electronic device such as a PDA (Personal Digital Assistant) that has a major feature of its portability, since the device is provided with a small display device, when the aspect ratio of the display screen is 16:9 and that of the main picture is 4:3, with the presence of the side panel portions as shown in FIG. 1, if the sub tile is displayed with an aspect ratio of 4:3, it may become difficult to watch the subtitle.